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  • Author Author: colporteur
  • Date Created: Date Created
  • Views 4712 views
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  • Comments 17 comments
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The Road to Raspberry Pi4B/ PoE Hat RoadTest Review (PoE insight needed)

colporteur

********************ISSUE RESOLVED. Credit to for identifying that a networking device was the issue.  ***********************

 

I would like the assistance of members that have PoE experience in reviewing my findings to help troubleshoot Ethernet failure under PoE.

 

I powered up the Pi4B & PoE Hat using a PoE power supply and managed to ssh over the wired Ethernet connection. Satisfied it worked, I command lined "sudo shutdown -h now" so I could teach go teach a class. When I cycled the PoE power supply on my return, the configuration failed to work. I determined Ethernet network was not being detected under PoE.

 

To isolate the issue, I ran a number of scenarios. I found it almost impossible to describe in writing the testing scenarios. Being a visual learner, pictures of each scenario seemed easier.  The attached drawing shows the hardware, connections and power status for each scenario. My interpretation of the results suggest the PoE power supply and PoE Hat are not at fault. The issue is with the Pi4B. Not working also means no indicator lights on the Pi RJ45 Ethernet Jack.

  • Compare scenario B & G: PoE power supply not at fault.
  • Compare scenario A & E & I: PoE Hat not at fault.
  • When you rule everything else out, what do you have left Pi4B

The PoE Hat controls the Pi Ethernet interface via the PoE headers. Would the PoE Hat have changed something (i.e. firmware/software) in the Pi4B when it detected PoE? It did work. I confirmed by checking logs. But only once.

 

An O/S re-install did nothing to resolve the issue.

 

If you look at the scenario's you will note the final scenario "J" using a Pi3B+ has not been ran. The scenario would use the PoE Hat to power the Pi3B+. The Pi3B+ is a personal device, not provided as part of the RoadTest. I am concerned running this scenario may render the Pi3B+ in the same state as the Pi4B.

 

Is the fault with the PoE Hat? Is it with the PoE power supply? Maybe it is the Pi4B? I am looking for individuals to review my findings and provide their insight.

image

  • in reply to kmikemoo

    Scenario I & G are confirmed. The Pi3B+ is Ethernet network enabled with the PoE power supply installed. The two onboard LED's for the interface are providing indication.

     

    Scenario B, C & E are not enabling a Ethernet connection on the Pi4B. No Ethernet indicator lights are lit in either scenario.

     

    Nothing has changed from my original findingsimage

     

    There is something wrong with the Pi4B PoE Ethernet detection. The network connection works, just not with PoE Hat or PoE power supply. Did the PoE Hat fry PoE support on the Pi4B when it powered up? If I power the Pi3B+ with PoE will I get the same results? If yes, then the PoE Hat caused the problems. If not then was the Pi4B weak from the beginning and failed during testing.

     

    Are there any tests that can be done from Pi GPIO to Pi PoE pins to see if everything is working? I have no knowledge on Pi PoE implementation so I'm in the dark.

     

    I am at the cross roads of applying PoE power to the Pi3B+ to see the results. I'm already into this RoadTest review for $100 purchasing the necessary power supplies, I really hate to invest more coin and toast a working Pi3B+ to get at the answer. It was so much easier to do this type of work when my employer was paying the billimage

     

    I'm going to let this blog post percolate for a few days, to see if there are any other responses.

  • in reply to kmikemoo

    Thanks M. I will try to duplicate your results. I'm not confident but with a fresh perspective maybe I may have some success.

  •   I cannot replicate the issue.  Initially, my unpowered PoE injector didn't pass signal.  Once I plugged it in and established communication through it, now it passes signal even when unplugged.  The only way I could hang the system was to have the PoE and USB-C powering the Pi and ssh shutdown.  Since it had two power sources, I couldn't power cycle the Pi - so it wouldn't restart.  Back to work.

  • in reply to kmikemoo

    Much appreciated M. I am on the cusp of jumping with both feet into the fire by powering up the PoE Hat on the Pi3B+.

     

    I would really like some insight into the PoE header on the Pi board. How does the Hat interact with the Pi? Did the Hat takeout something in the Pi4B? Can I do some kind of self test? Will the same thing happen on the Pi3B+?

     

    To think I walked around my house a few times with a box of CAT6 to get 328ft length of cable to run the ultimate PoE tests and not be able to do it is maddening.

  • in reply to colporteur

      Sean, that helps.  I'll see if I can replicate the issue (now that it's lunch time).  It's not the same equipment but it could be a quirk of the RPi4.  My RPi3's are at home.